apache Nifi getFTP regex filter?

[#1]

I want to import all files that are from A.

I want to import all files with this format [ABC_YYYYMMDD.txt] from FTP.

How should I express [File Filter Regex] field?

ex) abc_20200324.txt

[#2]

@mary_b 

You could use a Java Regular expression like this:

.*_(20)\d\d(0[1-9]|1[012])(0[1-9]|[12][0-9]|3[01]).txt

  The above will match everything before "_" and then must match a number that starts with "20", followed by  to digits "\d\d" (this matches any year in 2001-2099), followed by  "(0[1-9]|1[012])" (this matches months 01-09 or 10,11,12), followed by "(0[1-9]|[12][0-9]|3[01])" (this matches days 01-09 or 10-29 or 30 or 31), ending with the text string ".txt".

There are some good regex testers available on the web you may find useful.
https://regexr.com/
http://myregexp.com/
https://www.freeformatter.com/java-regex-tester.html

Hope this helps,

Matt